The long-term goal of this program is to understand, at the molecular level, the relationships between metal ions, oxygen metabolism, and oxidative stress, and their contributions to human health, aging, and disease. Central to this effort is the ability to track redox-active metal ions and oxygen metabolites in living biological systems. To meet this need, we will devise fluorescent sensors for copper and hydrogen peroxide, two major contributors to oxidative signaling and stress in the body, and apply these new chemical tools to study the roles of copper oxidation biology in genetic models of neurodegenerative and age-related diseases. Copper is a required redox-active cofactor for many oxygen-processing enzymes that regulate respiration, antioxidants, connective tissue, and neurotransmitter processing, but its cellular mismanagement can trigger oxidative stress through the unregulated production of hydrogen peroxide and related reactive oxygen species (ROS). Over time, subsequent oxidative damage to proteins, lipids, and nucleic acids can lead to the functional decline of tissue and organ systems in serious age-related human diseases, including cancer, cardiovascular disorders, and neurodegenerative diseases such as Alzheimer's disease (AD). H2O2 is more than a promiscuous ROS oxidant, however, as emerging evidence suggests that regulated production of this oxygen metabolite is critical for mediating events that control cell proliferation and/or cell death. The chemosensors devised here will provide powerful new chemical tools for tracking specific molecular species suspected of contributing to oxidative signaling and/or stress pathways. Specific aims include (i) developing selective and sensitive fluorescent sensors for imaging labile Cu(l) and Cu(ll) in living cells, (ii) devising analogous small-molecule reagents for selective live-cell imaging of H2O2, (iii) and applying these tools to study copper and peroxide accumulation, trafficking, and redox function in healthy and diseased cell and tissue models. Studying the basic science of metal nutrients and their interaction with oxygen metabolites in living systems is pertinent to understanding their contributions to serious diseases of public health. These efforts are of particular importance to diseases where age is a risk factor, including Alzheimer's and related neurodegenerative disorders, because they have high incidence of metal misregulation and oxidative stress.